Since a silicone composition forms a cured product having excellent weather resistance, heat resistance, hardness, and rubber properties such as extension, the silicone composition is used for protection of an LED element, an electrode, a substrate, and the like, in an LED device. In the LED device, conductive silver or silver-containing alloy is used as the electrode. In order to improve brightness, the substrate may be plated with silver.
In general, the cured product of the silicone composition has high gas permeability. When the cured product is used in a high-brightness LED which exhibits high light intensity and generates a large amount of heat, there are problems such as discoloration of a sealing material due to corrosive gases in an environment and a reduction in brightness due to corrosion of silver which is used as the electrode or with which the substrate is plated.
In order to solve the problems, a thermosetting silicone resin composition for sealing an optical semiconductor including a silsesquioxane, a silicone alkoxy oligomer, and a condensation catalyst has been proposed as a thermosetting silicone resin composition for sealing an optical semiconductor having excellent gas barrier properties (Patent Document 1).